Building the Great QRP Labs QCX Radio

Why I chose to buy the QRP Labs QCX Radio

I’ve been a Ham for over 45 years, but have never really gotten comfortable with Morse Code. Sure, I was able to pass the code requirement when I first got my Technician and later Advanced Class License, but my CW chops were always shaky at best. I had been more interested in building and modifying equipment anyway, so it didn’t seem like a major deficit. I also really enjoyed ragchews, and have fond memories of long conversations on FM repeaters.

Lately though, I’ve wanted to operate more CW. Amateur Radio has never been more diverse, and the digital modes are but one example of that diversity. I’ve tried several of them including PSK31 and FT8, but they lack the personal connection of talking directly with another ham. After a career in information technology, they also remind me too much of work. Perhaps I’m getting old, but restoring old gear and operating the historic modes is very appealing to me. In fact, I just recently posted on restoring an old Ten Tec Century 21 CW transceiver.

Action item: Work More CW

So how to improve? The obvious answer is to operate more CW. I’ve got plenty of CW capable rigs, but when SSB is available, it’s just too easy to use it. I’ve always been interested in the idea of low power (QRP). Tiny  radios that can be carried in a backpack or stowed in a Teardrop Trailer are appealing. So is building your own radio. Trouble is, I don’t feel qualified (yet!) to build a radio from scratch, and most of the QRP kits I’ve seen are either too much like a toy, are too expensive, or come mostly assembled already — plugging modules into a box.

If It seems too good to be true . . . Maybe it’s just a really good deal

Then I saw the QRP Labs QCX radio. At about $50, cost certainly isn’t an issue. They aren’t toys either. With a sophisticated Arduino-based design and clever use of digital amplifier modes, they pack an amazing amount of performance into a very small package. They can even be used as test gear; a Digital Volt and RF Power meter, Frequency Counter and Signal Generator. In terms of operating, these single-band radios include an Iambic Keyer, CW decoder, rotary encoder synthesized tuning and a WSPR Beacon. There’s a lot of capability here!

Quick Delivery and tiny goodness

After purchase, shipping from the UK is surprisingly quick. My 40-meter model arrived in just a few days. The kit includes a small circuit board and several poly bags with various parts. QRP Labs recommend a parts inventory first — if for no other reason than to identify the many very small parts.

There are two surface-mount ICs, but they come pre-installed on the multi-layer and beautifully silk-screened board. This is a very dense board with most of the components installed in the smallest possible space. For example, the resistors are all installed vertically. The holes are thru-plated and a solder mask prevents shorts for the most part, but a small-tipped soldering iron is a must.

This is a challenging build — RTFM

The QRP Labs assembly, theory of operation and instruction manual numbers no less than 152 pages. The writing is clear, and the order of assembly is determined by the relative size of the part. Lower profile parts are added first in order to maximize access for later part installation on the very crowded board.

Here’s a Pro tip: Double and triple check for the correct part and orientation before soldering. Parts are hard to remove due to their small size, and the process of removal could easily damage the board. A jeweler’s loop or magnifying glasses are a real help since the markings on many of the parts are so tiny. I found that using the magnifying camera app on my iPhone was helpful as well. Without those visual aids, I doubt my aging eyes could have seen well enough to complete the kit.

On the other hand, the instructions are really good

Toroidial transformer “T1” is installed first. It’s a little complicated with four windings, but the instructions are clear. It is important to note that phasing is critical, so following the instructions carefully is a must. There are many pictures that really help, and each assembly step is accompanied by a monochrome board diagram showing new parts in red. That makes it a lot easier to find locations for the many small parts. Work carefully and before long the wiring will be finished. Working in two-hour chunks, it took me about 14 hours to complete the kit.

Once complete, I powered the radio up. To my surprise, it worked right away. There was only one issue, the volume control didn’t seem to have much effect. Full volume! A careful check of the volume control terminals under magnification revealed a poor solder joint. Once repaired, the volume control worked as expected. Using the built-in test equipment, I went through the calibration process in just a few minutes.

You’ll be wanting a case . . .

You can use the board as is, but I wanted a case. A little scouting around the ‘net revealed a 3D printed case from W4mHz. His contact information is good on QRZ.com, and the case is $30 plus $5 shipping. Just drop him a line and he’ll respond with purchase instructions. He likes to have the case made before completing the transaction. Well worth it. I had the case in a few days, and it fits the QCX like a glove. You can see in it in the featured image above. Here’s a video describing the case from Mike:

A lot of fun to operate!

What a fantastic rig! I added a 12 volt gel cell for power, an antenna and tuner,  a set of Apple earbuds (like they ship with their iPhones), and a couple of of cables to make a complete 40 meter HF Go Bag. The direct conversion receiver works well, the transmitter delivers almost 4 watts on a fully charged gel cell (about 13.8 volts).  Add a small solar panel and charge controller and you’ve got a complete power solution for indefinite remote operation. Add a QRP antenna and tuner and you’ve got an effective radio system for SOTA activations, emergency use or just plain QRP fun. With some added test leads and the built-in test gear, you could also service other equipment in a remote setting. If I could buy just one radio for my remote use, this would be it. Now the question is; which band is best . . .